The present invention relates to a vapor phase processing apparatus for performing a vapor phase process, e.g., film formation, on a substrate, e.g., a semiconductor substrate, in accordance with CVD.
In a semiconductor device, a conductive or insulating thin film is formed on a substrate. As such an insulating film, for example, an SiO.sub.2 thermal oxide film, or an SiO.sub.2 film or SiN film formed by using a source gas, e.g., silane or tetraethoxysilane (TEOS), at a reduced or atmospheric pressure in accordance with chemical vapor deposition (CVD) is mainly used.
CVD is a film formation method which is widely used in the manufacture of a semiconductor device as a method of forming a conductive or insulating thin film on a substrate. In particular, plasma CVD is often used since it enables film formation at a comparatively low temperature.
In recent years, the diameter of a silicon wafer serving as the underlying layer of a semiconductor device increases. In general, a CVD apparatus used for forming a thin film on such a large-diameter silicon wafer uses, as a member which supplies a source gas, a dispersion nozzle having a plurality of source gas supply holes, so that a uniform thin film can be formed.
The diameter of the gas supply holes of the dispersion nozzle used in the CVD apparatus described above is very small (e.g., about 1 mm). A deposit tends to attach to the inner portions of the holes during a film formation process, causing clogging. If such clogging occurs, the gas supply amount onto the wafer becomes nonuniform. As a result, the film formation speed, the film composition, and the like on the wafer vary.
In order to decrease these variations, conventionally, every time a desired thin film is formed on one or a plurality of semiconductor substrates, the inner wall of the processing chamber or the dispersion nozzle is cleaned by using an etching gas, thereby removing the deposit. With this chemical interior cleaning, however, the deposit cannot sometimes be sufficiently removed. If the film formation process is repeated, the deposit is accumulated, and a sufficient cleaning effect cannot be obtained with only the chemical internal cleaning described above. Therefore, conventionally, not only chemical internal cleaning is performed, but also the processing chamber is opened, disassembled, and cleaned in the atmosphere periodically.
Conventionally, it has not been precisely grasped regarding to what extent the film formation process can be repeated until when chemical internal cleaning is to be performed (when chemical internal cleaning should be performed), how long chemical internal cleaning should be performed (when chemical internal cleaning should be ended), to what extent the film formation process can be repeated until when the processing chamber is to be opened, disassembled, and cleaned in the atmosphere (when disassembly and cleaning in the atmosphere should be performed). In other words, conventionally, these matters are determined based on the experience, the in-surface uniformity of the deposition speed of the film formed on the semiconductor substrate, and the like.
Therefore, much time has been conventionally spent on chemical internal cleaning, disassembly and cleaning, and the like. Conventionally, internal cleaning using an etching gas is excessively performed in order to prevent insufficient removal of the deposit. As a result, portions in the processing chamber that have low durability tend to be damaged, and damaged components must be exchanged often. Also, dust tends to be generated easily.